What's that crosshair in the 3D View?
Firstly, the 3D cursor doesn't interfere with selection.
By default LMB places the cursor, RMB selects.

The crosshair is the 3D Cursor, it is like a cursor in a text-editor it shows where Blender will put stuff and also where the center of some operations can be set to be performed from, such as scaling, rotating, the pivot point when bending, the depth grease pencil is drawn and a point you can use to snap the selection to.

While it may seem strange at first, when you start using Blender but it becomes an indispensable tool when you get more experienced.

Here is a link to the blender manual describing the 3D cursor. https://www.blender.org/manual/editors/3dview/3d_cursor.html

Here is a quick video that will help you better understand how it works. https://www.youtube.com/watch?v=Nlk28Ex9jVQ